How long have you been stuck on processing? It was stuck for me for a few mins before giving me a card error, then I was able to re-enter payment info.
Just try clicking checkout every 5-10 sec, not too fast or it'll block you. This worked for me and I was on checkout for at least 5 mins. I didn't refresh the page at all.
For whoever is on checkout loop, give it 5-10 seconds before clicking checkout again. I got blocked out on my regular browser and was able to re-do it on incognito mode in Chrome.